Heat oven to 400 degrees. Stuff the hens with onions. Brush all over with honey; cover the breast of each with 3 slices bacon or pancetta. Settle into a roasting pan. Toss the leeks with the oil; add to the pan, tucking them in around the birds. Season with the salt and pepper to taste. Roast 45-60 minutes. If the bacon begins to blacken, cover hens with foil. Remove the birds from the pan; keep warm. Using a slotted spoon, transfer the leeks to a serving dish; keep warm. Tilt the pan to one side; skim away any fat. Pour a little hot water into the roasting pan; set over high heat. Heat to a boil, scraping up any crispy bits from the bottom of the pan; simmer for a few minutes. Pour the pan sauce into a gravy boat or pitcher; serve with the hens and the leeks.